In many different technical fields of today, there is a need for being able to remotely open up a volume with an extremely high degree of confidence. Examples can be found in space technology, in biochemical production or in drug related applications. In many of these applications, the opening of the volume is a one-shot action, i.e. the volume is not intended to be closed any more. In such applications, so called single use valves are typically used. However, the time elapsing before opening the valve may be very long. In space applications storage times of several years are not uncommon, which calls for seals with essentially no leakage at all. Furthermore, many applications also require any such single use valves to be of a small size.
One example of a single use valve intended for biochemistry applications is disclosed in [1]. Here a hole in a glass plate is covered with a PE/PET film, in which a flap is etched. The flap is adhered to the glass plate. By sending a current through a coil provided around the hole, the adhering of the PE/PET flap is reduced, and any overpressure on the inlet side of the plate will force the flap to bend out at the outlet side of the plate and thereby open a free passage. One disadvantage with such an arrangement is that it is difficult to ensure a tight seal from the beginning. Another disadvantage is that debris particles from the film and/or the adhering material may be removed from the valve and follow into the flowing gas stream. Yet another disadvantage is that this arrangement can only be used for sealing relatively low pressure differences.
Such problems are avoided in a valve disclosed in [2], intended for fluid systems in space applications. A channel is etched in a silicon wafer and covered by a glass plate. A thin plug of silicon is left over the channel, in order to provide a safe seal. The plug is doped to enhance its electrical conductance. Metal leads are deposited on the silicon wafer to connect the two ends of the plug. By sending a current through the plug, the silicon is caused to melt and thereby open a passage through the silicon channel. The channel is provided with bends to trap plug debris, preventing it from leaving the valve. A disadvantage with such a solution is that if the plug cracks with a thin crack or the melting of the plug becomes very local, the opening provided in the channel may not be very large, and at least not controllable. However, the current is prohibited to be conducted through the broken plug, and no further opening can be achieved.
It is not technically possible to combine [1] and [2], since the first one is based on that the flap covers the exit hole of the valve, while the latter requires the plug to be positioned at the inlet of the valve, i.e. before the debris traps.